The invention relates to a device for measuring values from a person lying down, in particular the movement, direction of movement and/or vital parameters of this person, using sensors. The invention also relates to a method for measuring values of this nature. Finally, the invention relates to a pressure sensor having a sensor element.
It is known to measure pressure values of body parts of a person lying on a mattress. Measurements of this nature are used primarily to prevent decubitus. A device which is known from DE 42 40 782 A1 for this purpose has a multiplicity of sensors, namely 33 rows of in each case 23 sensors, making a total of more than 600 sensors, which measure the compressive loads and transmit measured values obtained to an evaluation unit.
This known device has the drawback of being susceptible to faults, on account of the large number of sensors. Furthermore, each individual sensor has to be calibrated, so that the measurement results from the individual sensors can be compared with one another. This requires a very high level of outlay, in particular since this calibration has to be repeated at specified maintenance intervals.
The invention is therefore based on the technical problem of improving the measurement of values from a person lying down.
To solve this problem, a device of the type described in the introduction is characterized in that sensors are arranged in the region of the thorax and/or the sacrum. Furthermore, the problem is solved by a method for measuring values from a person who is on a device of this nature, in which measured values from the sensors in the region of the thorax and/or the sacrum are measured and recorded continuously.
According to the invention, the sensors are arranged in that area of the device in which the chest of a person lying on the mattress is situatedxe2x80x94the area known as the thoraxxe2x80x94and/or in the area in which the abdomen of the person is situated, the region known as the sacrum. As a result, the sensors are situated in the region of the centre of gravity of a person lying on the mattress. This advantageously enables movements and the direction of these movements by the person to be detected. Furthermore, arranging a sensor in the region of the thorax also advantageously enables the heartbeat and the respiration of the person to be detected.
It is preferable for pressures to be measured using a sensor cushion and to be evaluated in an evaluation unit, in that absolute pressures from the sensor cushions and/or relative pressures between a plurality of sensor cushions are combined in a calculation, in order to determine a movement, the direction of this movement and/or vital parameters of the person.
A pressure sensor according to the invention is characterized in that the pressure sensor has a sensor cushion which is filled with a gaseous or liquid medium, it being possible for a pressure which can be exerted on the sensor cushion to be transmitted via the medium to the sensor element. In this context, the term xe2x80x9cpressure sensorxe2x80x9d is to be understood as meaning a (relatively large) arrangement having a cushionxe2x80x94the sensor cushionxe2x80x94and at least one sensor element (which is relatively small in the context of this arrangement).
A pressure sensor according to the invention arranged in or on the device or mattress according to the invention offers the advantage of itself increasing the pick-up area and therefore the measurement range of a sensor element by a multiple compared to the pick-up area of the sensor element. For this purpose, the pressure element is connected to a cushion which is able to transmit a pressure exerted by a person who is on the mattress to the sensor element. Overall, the connected sensor cushion leads to an increase in the surface area of the sensor element. As a result, it is sufficient to equip a mattress with only a small number of, in particular two to four or five, pressure sensors, while nevertheless obtaining measurements which cover a large area of the mattress.
The cushion is preferably enclosed by a liquid-tight and/or airtight cover and is filled with a gaseous or liquid medium which transfers the pressure to the sensor element. This medium may in particular be air, water or a gel-like substance.
Preferably, the sensor cushion is also filled with an elastic material, for example foam. This is particularly advantageous in the case of an air-filled sensor cushion. This is because the filling with the elastic material means that the sensor cushion always returns to its optimum shape. This applies even if the inherently airtight cover has become air-permeable, for example as a result of slight damage, which would cause a cushion filled only with air to collapse. A pressure measurement using a sensor cushion of this type can then be carried out even if the cushion cover is slightly damaged.
It is particularly preferable for the sensor element not to be arranged directly on the sensor cushion, but rather to be connected to the sensor cushion via a hose or a flexible capillary. This has the advantage, inter alia, that the sensitive sensor element can be accommodated at an area (of the mattress) which is subjected to little or no mechanical load.
The advantageous evaluation of the absolute pressures on the sensor cushions and/or the relative pressures between a plurality of sensor cushions enables various data concerning the person on the mattress to be recorded. In particular, a combination of an absolute pressure measurement and a measurement of the relative pressure changes and the temporal profile thereof enables movements of a person on the mattress to be detected. In particular, the invention makes it possible to establish whether a significant change in position has actually taken place during a movement, for example from a position in which the person is lying on his side into a position in which he is lying on his back, or vice versa, or whether the movement was only, for example, a leg movement or an external manipulation of the bed or the mattress without a significant change in the bodily position of the person. This question is of importance if a mattress is to be used for preventing decubitus.